EP1307643B1 - Method and device for controlling a drive unit - Google Patents

Description

State of the art

The invention relates to a method and a device for controlling a drive unit.

From WO99 / 13207 is a method and an apparatus for controlling a drive unit a vehicle known, wherein on the basis of the driver's request, a target torque value or a target power value is formed, which is used to control the drive unit serves, with a maximum allowable torque or a maximum allowable power is determined and the setpoint is limited to the maximum permissible value, if it exceeds the maximum allowable value. The maximum allowable moment is usually greater than the allowable torque used to limit it. A filtering is to increase the intake manifold time constant, the position controller delay and the moments Functions, such as B. Dashpot.

Such a method and such a device is known from DE 195 36 038 A1 (U.S. Patent 5,692,472). There is in the context of the control of the drive unit a motor vehicle for monitoring purposes one an output of the drive unit representing size with a maximum allowed for this size Value compared, where error response measures are initiated when the Size exceeds the specified allowable value. Examples of the output size the drive unit are the power of the drive unit or a torque of the drive unit, For example, the indicated torque, the output torque, etc. In one embodiment, the controller executes the control of the drive unit Computer at least two separate program levels, the calculated comparison for monitoring purposes in the second program level becomes. The first program level is reserved for programs that support the Calculate control of the drive unit provided functions. In another execution in the first program level Limitation of the default value controlling the drive unit made to the maximum allowable value.

In order to determine the maximum permissible value, it is generally if there is no driver request, the largest occurring value of the output caused by the idling control can be set, given. Thereby unrestricted driveability is guaranteed. In front especially in vehicles with small engines, low rolling resistance or low internal friction affect consumers like an air conditioning compressor, a torque converter, etc. very strong on the output size of the drive unit, so that with regard to the driveability relatively large permissible Values are to be specified.

To improve the accuracy of the determination of the permissible Value of the output is according to DE 197 39 565 A1 for the Nachstartphase with cold drive unit an expansion of the maximum permissible value, whereby Additional functions can be unaffected in this area and at the same time outside this range a relative exact specification of the maximum permissible value and therefore achieved a great effectiveness in error detection becomes. However, with this method only two operating states distinguished.

From the not previously published German patent application 199 63 759.8 dated 30.12.1999 is known to determine the permissible value a weighting with the maximum permissible value Driver's request between a maximum and a minimum to calculate the permissible value. This will be additional via a separate path the permissible requirements of Consumer and the idle controller tested and taken into account. If these shares are calculated incorrectly, they will become limited.

The described known solutions do not show in all Optimal results as they match the subject matter can be achieved according to the independent claims 1 and 9, respectively.

Advantages of the invention

The advantageous use of so-called splines is advantageous Way a continuous, gentle reduction the permissible values of the output variable in critical operating states reached the engine. This has in comparison to a conventional, bit-driven reducing the advantage that the reduction does not happen abruptly and so on the danger of vibrations and of the driver as too violent perceived load impacts is avoided.

The reduction of the permissible values of the output variable takes place in a preferred embodiment in the each error case, in other embodiments only in selected, at least when the output increasing Errors are perceived by the driver as particularly disturbing i.e. with the accelerator pedal released and one above the Idle speed located speed and / or if the brake has kicked.

When reducing the allowable values of the output a characteristic is used which depends on engine speed is and which is designed such that at greatly increased The permissible values of the output value are 0 to reach. As a result, even with smooth running engines acceptable error responses achieved. It is particularly advantageous that when the brake is kicked permissible value of the output is reduced and that Vehicle is easier to brake in case of failure.

Of particular advantage is the introduction of a dead time the filtering of the allowable values of the output, as a result takes into account the suction tube dead time of the intake system becomes. This leads to a simplified application of the used Filter constant and that an optional existing dashpot feature is not restricted.

Furthermore, advantageously by an initialization this filter at reduction of pedal travel one faster error response achieved. This is especially true in case of an error in which a maximum driver request is given. This error may accelerate come up to the maximum speed, the improved filtering reduces such overshoots, due to initialization about reduction of pedal way the Vibration tendency of the motor significantly reduced in the event of a fault is.

Particular advantages arise in systems in which permissible values of the output variable in two program levels, Level 1 and Level 2 are formed. The reduction the permissible values of the output variable using splines is carried out only in the level 1, so that the application effort is significantly reduced. Furthermore, will by initializing the filter by means of the pedal travel signal a much faster error response straight in Level 1 is reached while the overshoots in the level 2 are reduced in the mentioned error case.

Furthermore, a consideration of additional torque requirements in cold start, e.g. at Connecting additional consumers or control functions. This leads to improved availability while at the same time Improve the accuracy of the monitoring.

Further advantages will become apparent from the following description of embodiments or of the dependent Claims.

drawing

The invention will be described below with reference to the drawing illustrated embodiments illustrated. It shows Figure 1 is a block diagram of a control unit for control the drive unit of a vehicle. In the figures 2 and Figure 3 are flowcharts which are preferred Embodiments for determining the maximum permissible value the output of the drive unit, in particular their Moment, pose. In Figure 4, the consideration additional torque requirements in cold start at calculation of the minimum permissible torque as a flowchart shown.

Description of exemplary embodiments

FIG. 1 shows a control unit 10 for controlling a drive unit 12, wherein the control unit 10 at least one Computer including memory includes, in which the control the drive unit 12 serving programs are stored. To carry out these programs are the calculator over Input lines 14 to 18 of corresponding measuring devices 20 to 24 operating variable signals of the drive unit and / or the vehicle supplied, which is evaluated by the computer and in the formation of the at least one actuating signal be considered for the drive unit 12. such Operating size signals are e.g. Signals indicating the engine temperature, Accelerator pedal position, etc. represent.

The input to the control unit 10 are input by means of running in the computer programs in at least implemented a manipulated variable, which over the at least one Output line 40 of the control unit 10, the at least one State variable of the drive unit 12 in terms of the input variables controls. In the preferred embodiment is off the input variables, in particular accelerator pedal position and engine speed a setpoint torque as the setpoint for an output variable determined, which in control signals for control the throttle position, the ignition angle and / or the Fuel metering, etc. implemented an internal combustion engine is, wherein the torque of the internal combustion engine (ie their Output) approaches the predetermined setpoint.

Instead of a torque is in another embodiment the power of the drive unit, its speed, etc. controlled as output accordingly. The The procedure described below is not limited to Connection with an internal combustion engine, but also at other drive types, e.g. used in electric motors.

In the preferred embodiment, a division of Programs are provided in at least two levels, with the First level programs are assigned to the control function and perform the above-mentioned setpoint limitation, assigned during the second level monitoring programs are, which also in the aforementioned state of Technology are described.

To calculate the maximum allowable value for the output the drive unit becomes a maximum allowable Value determined depending on the engine speed. Base of the minimum Value form the determined depending on the engine speed maximum permissible values of the output quantity at released pedal, by means of a correction value for the cold start phase, which depends on engine temperature and Engine speed is formed, a correction value when active Catalyst heating function, which also depends on the speed is corrected and / or allowable consumer demand values becomes. The latter represent the maximum permissible demand values the active consumer and / or a power stabilization function. These values become minimal permissible output value combined. For determination of the maximum underlying the comparison for monitoring permissible value of the output variable becomes the maximum permissible Value resulting from accelerator pedal position and engine speed according to specification a map has been determined between the above described minimum and maximum allowable value weighted, preferably interpolated.

In this way, an accurate determination of the maximum allowable Value of the output of the drive unit reached, based on the above-mentioned monitoring lies. The procedure described is both in the formation of the maximum permissible values in level 1 as well as in level 2 instead.

In the event of an error, the permissible values of the output variable are tightened, ie reduced. This tightening does not happen abruptly, but continuously and gently via so-called splines. These allow transition states to be defined so that not only black-and-white states but also gray zones are present. The first-order splines have the following general formula, where the input variable is the variable X, the output variable is the variable Y and the transition region is designated by ε:

The output signals of several splines can be like bits with each other be linked. A multiplication represents one logical AND, an addition logical Or link is.

In addition to splines of the first order, higher-order splines can also be used, which, however, represent an increased amount of computation. As an example of a second-order spline, the following general equation is given:

By a spline of second order is also steadiness in the first derivative guaranteed. The danger, vibrations to stimulate, is thereby further reduced.

In the present application, the splines are used, by the permissible value in certain operating conditions to control and reduce sharper. Such a Operating condition is when the pedal angle is 0, i. the accelerator pedal is released and / or the brake is kicked when the speed is greater than the idle speed and / or if the desired air or ignition torques are the maximum exceed permissible torques.

The latter condition is only in a preferred embodiment present, may be omitted in other embodiments be.

By linking these conditions with the splines an error indicator is received. Approaching one of the Input values of the splines of their border down to the applicable one Gray zone in, so delivers the relevant spline Values between 0 and 1. The error indicator then returns from 0 different values, if all conditions are at least in their gray areas. Depending on the value of the error indicator is then of the permissible outputs deducted a value to be applied. Are all conditions is satisfied, the value of the error indicator is 1. Then the largest applied value subtracted from the allowed values and the error response in this way more manageable.

Furthermore, when determining the permissible values, besides The filtering introduced a dead time, which is the Saugrohrverhalten considered. Filter and dead time are replaced by a Reduction of the pedal travel initialized. Further, at the determination of the permissible value according to the following Description of the minimum fillings of an internal combustion engine considered.

In the figures 2 and 3 flowcharts are shown, which is a preferred embodiment for determining the maximum permissible value of the output variable, in the preferred Represent embodiment of the maximum allowable torque. The individual blocks designate programs, program parts or program steps while connecting lines represent the flow of information.

Off.den supplied sizes pedal position WPED and engine speed Nmot is in a first map 100, the maximum permissible Driver request torque MIFAZUL formed. It also becomes dependent from the engine speed and the engine temperature Tmot in 102 a minimum allowable moment MIMINZUL formed while in 104, for example, based on the engine speed maximum permissible maximum torque MIMAXZUL is determined.

Definition of the minimum and maximum allowable moments is essentially from the above-mentioned prior Technique known. In a preferred embodiment the maximum permissible moment is calculated from the smaller value of the speed-dependent maximum read out of a characteristic curve permissible moments and actually in the past occurring maximum moments formed.

At the minimum torque, a cold start reservation is additionally included in the cold start activated additively depending on the engine temperature, depending on the engine temperature filtered in time different proportions are taken into account. Thereby the maximum allowable torque will eventually be in cold start expanded so that the availability of the vehicle in this Area is less restricted.

In 106, a provisional value of the maximum permissible value is then entered Moments MIZUV formed according to the weighting of the maximum allowable, relative driver torque MIFAZUL and between the minimum and maximum allowable moment. The preliminary maximum allowable moment MIZUV is then a deadtime element 108 supplied. The dead time is at the dead time the intake manifold system of the internal combustion engine oriented or corresponds to this dead time. The provisionally permissible moment is then fed to the deadtime member a low-pass filter 110 and filtered there. Output signal is the filtered one maximum permissible moment MIZUFIL. The filtering is initialized, if a return of the accelerator pedal has been detected. This is done by a corresponding threshold switch 112, which is supplied with the pedal position signal WPED is. It generates an output signal when the accelerator pedal is withdrawn is, i. e.g. if this is a threshold below. The output signal leads to a Initialization of the filter 110 with the provisional maximum permissible value as well as a switching of the switching element 114 in the dashed line position. These Position means that the filtered maximum allowable Value is output. It is further provided, the filter 110th then initialize when external torque requests be present, for example, requirements of a motor drag torque controller, a traction control, etc. In this Case is used as the second initialization size instead of the Return of the accelerator pedal position the withdrawal of the provisional maximum permissible torque MIZUV evaluated. Further In a predicate 116, the filtered maximum permissible moment MIZUFIL compared with the unfiltered MIZUV. If the unfiltered is smaller than the filtered one, so is via the output line of the comparison element 116 the Switching element 114 shown in the solid line Switched position. This means that then instead of the filtered maximum permissible torque the unfiltered is passed on.

Similarly, the dead zone member 108 is connected to the provisional value initialized.

As a rule, therefore, the unfiltered for further processing maximum allowed moment passed, if not a return of the accelerator pedal has been detected. In this case the maximum permissible moment is filtered, since the withdrawal the accelerator pedal only after a certain dead time makes the torque noticeable with a delay. To prevent, that too fast a reduction of the maximum permissible Moments and thus too fast an error reaction occurs This is filtered via deadband 108 and filter 110 maximum allowed moment passed, taking at initialization from Totzonenglied and filter the unfiltered moment is set as the starting point. Once the filtered smaller as the unfiltered moment is, the unfiltered one again passed.

The permissible moment MIZUL formed in this way becomes then further processed according to FIG. In FIG. 3, the continuous reduction of the maximum permissible torque represented in certain operating situations, the be used initially mentioned splines. First, will however, the maximum allowable torque value of a maximum value selection stage 118 supplied, in the one of the engine speed Nmot dependent value formed by means of a characteristic 120 is, and which the minimum filling of the internal combustion engine represents compared to the maximum allowable value and the larger each passed. Is the accelerator pedal let go, i. the accelerator pedal position equals 0, so is output from the signal generator 122, a signal which the switching element 124 is in the dashed position and the maximum value selection 118 supplies the value 0. That on this Way possibly limited maximum permissible moment becomes then one Differential point 126 supplied in the in the corresponding Operating conditions a continuously variable Value is deducted and in this way the maximum allowable Moment is reduced. Output signal of the differential stage 126 is the maximum allowable moment MIZU, which is in a Reference junction 128 compared with the actual moment MIIST is, wherein when exceeding the maximum allowable torque by the Istmoment error response measures, for example a limitation of the torque setpoint, a shutdown of the Fuel supply, etc. are initiated.

To determine the Reduzierfaktors, which in the differential stage 126, the above-mentioned Used splines. In Figure 3 is a preferred embodiment shown in which a reduction takes place when the accelerator pedal is released (pedal angle WPED equals 0) or the brake has kicked or the speed Nmot is greater than the stationary target speed. Besides In one embodiment, the desired torques for the air and the Zündwinkelpfad with predetermined limits compared, whereby when exceeding the permissible value by one of the two set torques also a reduction the maximum permissible torque occurs. The realization with splines is made accordingly, where for the set torques form additional criteria. In a characteristic 130 becomes a correction factor depending on the engine speed formed for the maximum allowable moment, which in multiplication point 132 with a value between 0 and 1 multiplied. The weighted correction value MIKORR is supplied to the difference point 126. Further, in FIG 3, two spline functions 134 and 136 are shown after the formula given above for a first-order spline work in another embodiment second order. The input of the spline 134 is formed from the Difference between the pedal travel WPED and a pedal threshold WSCHW, the area of the released accelerator pedal delimited from the area of the stepped accelerator pedal. The difference is formed in the difference stage 138. The value ε is the threshold WSCHW. The output Y of the spline function 134 is in a multiplication 140 with the Output value of the spline function 136 linked. This link As mentioned above, provides a logical AND link output of multiplication 140 is the error value ERRIND, which takes values between 0 and 1. Values greater than 1 are limited to 1. The input quantity of the second illustrated spline 136 is the difference between engine speed Nmot and stationary idle speed Nstat, which formed in the point of difference 142 becomes. The value ε depends on a characteristic 144 determined by the engine temperature Tmot. The output size Y 'of the spline 136 is in an addition point 146 the value 1 is activated when the brake is applied, or the value 0 when the brake is not applied. The initial value the addition point 146 becomes the multiplication point 140 led.

Thus, as mentioned above, by the splines in the case that their input quantity enters the gray area ε, a value formed between 0 and 1, with input quantities below the gray area the value 0 is the output the splines is above 1. If the value deviates from 0, so becomes dependent on engine speed in multiplier 132 Correction value switched to the maximum permissible torque, weighted according to the extent of entry the input variables in the gray area, where at the end the gray area when the threshold is reached, the output value assumes the value 1. Thus, when approaching to the stated operating conditions the maximum permissible Moment continuously reduced.

FIG. 4 shows a flow chart for determining the minimum permissible moments, taking special measures for the Cold start and the additional torque requirements in this Operating state are met. The minimum allowed Moment miminzul becomes dependent on the engine speed nmot e.g. predetermined by a characteristic 200. This size becomes a nonzero value in link 202 switched on (preferably added), if certain predetermined Conditions exist. These are in the switching signal B_zusatz summarized, with this switching signal a positive Has value if additional torque requirements e.g. additional consumers such as vacuum pumps, Air conditioners, fans, headlights, from the generator, etc. are present request the extra moment, and / or additional Functions that also increase the momentum lead the drive unit, such as a Katalysatorheizfunktion. Preferably, the switching signal B_zusatz only on set a positive value if such a torque request during the cold start phase or after start phase occurs. Does the switching signal have a positive value, the switching element 204 is transferred to the dashed position. In this operating state is in the linkage 202 the speed-dependent value a speed and motor temperature dependent formed value switched. The latter is e.g. in map 206 depending on engine speed nmot and engine temperature tmot formed. He takes into account the additional losses occurring in cold engine e.g. through increased friction. This value is in the link 208 with additional torque requests values switched (preferably added) containing these additional Consider torque requirements. So becomes active Catalyst heating function (condition B_katheiz fulfilled) further speed-dependent value in the point of connection 208 activated. This value is e.g. in a characteristic 210 determined depending on the engine speed nmot and switched on, when the switching element 212 in the presence of said Condition in the dashed position is located.

Another value to be added in the node 208 is formed in the filter 214. This preferably represents a low-pass filter in which a motor temperature-dependent value formed in 216 is filtered. In 216, the engine temperature tmot is read in and set with respect to a fixed temperature value TNS, possibly weighted with further predetermined variables. The temperature value represents a limit that distinguishes the operating state of the cold start from others. In the preferred embodiment, the signal dm_zusatz applied to the filter is formed as follows: dm_supplement = (TNS - tmot) * dmzul / Δmns where dmzul and Δmns are fixed preset weighting quantities.

The low-pass filter is designed such that filtering only takes place when one positive edge was detected in condition signal B_addition (see 218), i. only at Occurrence of a new moment request. The value at this time dm_zusatz is filtered with a certain time constant, with changes of this Value can not be taken into account after the above date. The filtered one Value dm_zusatz thus represents a time filtered engine temperature-dependent proportion (Cold start derivative).

The described determination of the minimum allowable torque takes place both in plane 1 as well as in level 2.

Claims (11)

1. Method for controlling a drive unit, in which a maximum value of an output variable from the drive unit is defined and, if this maximum value is exceeded by the current value, measures are initiated, the maximum permissible value being formed on the basis of the accelerator pedal position and, in at least one operating state, been filtered on the model of the dynamics of the intake pipe of an internal combustion engine, characterized in that the filtering comprises a dead-zone element which represents the dead time in the intake pipe.
2. Method according to Claim 1, characterized in that the filter and/or the dead-zone element are initialized when a release of the accelerator pedal is detected.
3. Method according to one of the preceding claims, characterized in that the maximum permissible value is the filtered value when a release of the accelerator pedal is detected, while it is the unfiltered value if the filtered value becomes smaller than the unfiltered value.
4. Method according to one of the preceding claims, characterized in that the maximum permissible value is reduced continuously, depending on the margin between at least one variable indicating a specific operating state and a limiting variable.
5. Method according to Claim 4, characterized in that what are known as splines are used to determine the magnitude of the reduction.
6. Method according to Claim 4 or 5, characterized in that the permissible value is reduced when the accelerator pedal is released or the brake is applied and the engine speed is greater than the desired speed at idle.
7. Method according to one of Claims 4 to 6, characterized in that a limiting variable for the accelerator pedal position and/or the difference between the engine speed and desired speed is formed and, when it is approached, an output variable is determined which becomes greater with increasing approach and which acts on the corrective value to reduce the maximum permissible value.
8. Method according to one of the preceding claims, characterized in that this maximum value is determined on the basis of the minimum charge and/or in that this maximum value is determined on the basis of a minimum value which, when there is an additional torque requirement, is formed by means of an engine-temperature-dependent value.
9. Device for controlling a drive unit, having a control unit which forms a maximum permissible value for an output variable from the drive unit and, if this maximum value is exceeded by the current value, initiates reaction measures, the maximum permissible value being formed on the basis of the accelerator pedal position, characterized in that the control unit comprises filter means which filter the maximum permissible value, the filter means comprising a dead-zone element derived from the intake pipe dead time.
10. Device according to Claim 9, characterized in that the control unit comprises corrective means which reduce the maximum permissible value continuously on the basis of the approach of at least one variable representing an operating state to a limiting variable.
11. Device according to Claim 9 or 10, characterized in that the control unit has means which determine this maximum value on the basis of the minimum charge and/or which determine this maximum value on the basis of a minimum value which, when there is an additional torque requirement, is formed by means of an engine-temperature-dependent value.

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